* 値 [CODE(JS)@en[NaN]] (JavaScript)

[1]
>The [[primitive value]] [DF[[CODE(JS)@en[NaN]]]] represents the [[set]] of [[IEEE Standard]] 
"[[Not-a-Number]]" [[values]]. This [[value]] is a [[member]] of the [CODE(JS)@en[[[Number]]]] [[type]].

;; [CITE[ECMAScript Language Specification (HTML version)]] ([TIME[2009-04-03 04:43:48 +09:00]] 版) <http://bclary.com/2004/11/07/#a-4.3.23>

[2]
:名前:[CODE(JS)@en[[[NaN]]]]
:型:[CODE(JS)@en[[[Number]]]]